One widely used method for forming a pattern such as metallic circuitry on a substrate in the manufacture of printed circuit boards in integrated circuits is to imagewise form a pattern of photoresist material over those areas of the substrate or over a metal-coated substrate to be shielded from metal deposition or metal removal. The photoresist layer is normally formed of a polymeric, organic material that is substantially unaffected by the metal deposition or metal removal process and, accordingly, protects the underlying areas.
The pattern is formed by imagewise exposing the photoresist material to actinic light through a photographic image, such as a glass master, by photolithographic techniques. The actinic light employed is usually X-ray, U.V. radiation, or electron beam radiation.
A number of photoresist materials are well-known and are capable of forming desired masking pattern. However, providing compositions which exhibit acceptable imaging (resolution and acuity) characteristics to be suitable as an image or pattern mask, especially for integrated circuits, along with the ability to tailor the composition to providing either a positive or negative resist, is quite unusual.
Also, providing such compositions with the ability to achieve a permanent protective coating is even that much more difficult.
In the manufacture of printed circuit boards and cards it is desirable that the photosensitive material used be patternable by means of photolytic process as is the practice with photoresists and which also, unlike most photoresists, can be retained to perform one or more additional functional uses during or after fabrication of the circuit board.